We mammals are all very hairy, there’s no denying that. But compared to our close primate cousins, chimpanzees and gorillas, humans are practically bald. What noticeable hair we do have is mainly reserved for our scalp and, once we go through puberty, our groins and our armpits.

Our minimally hirsute nature is puzzling, but there’s a pricklier question hiding just below our eyes: why do men, but not women, typically have so much hair on their faces?

The hormonal picture

Everyone has facial hair, male or female. But the facial follicles of (biological) men usually produce thicker, darker hairs that can sometimes end up as substantial beards if not trimmed back regularly.

Turns out this happens in men because facial hair follicles respond aggressively to testosterone, the sex hormone abundant in men.

Because of this hormonal difference, the beard, or facial hair more broadly, is a classic secondary sexual characteristic — a trait that differs between the sexes, but does not directly contribute to reproduction like, for example, the genitals do.

There are many examples of such characteristics in humans: on average, men have beards and thicker body hair, while women have breasts and wider hips.

Sexy beards

Beards are not even unique to humans. “Facial hair exaggeration is not uncommon in mammals — lions famously have manes — and a lot of the primates have facial hair embellishments, like a greying of the facial hair,” says Professor Rob Brooks, an evolutionary biologist at the University of New South Wales, who studies evolution and sex.

The lion-tailed macaque (Macaca silenus) wants you to check out his mane.

The lion-tailed macaque (Macaca silenus) wants you to check out his mane.

“There are two main processes that shape the evolution of sex-dependent traits” like beards, says Brooks. “One is if it gives you an advantage in competition with other members of the same sex, and the other is that it makes you attractive to members of the opposite sex.”

Beards may slot into both categories, and so probably aren’t a random accident of evolution — there is decades-worth of research into the role they can play in governing human behaviour between men and women, and between men and other men.

So, are beards always sexy to women who are into men? “The answer is very patchy,” says Brooks (perhaps not realising the pun he made). “Some women really like it, some women really don't, and some women are neither here nor there on the whole thing: it's not like there's a universal liking for beards among women.”

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Men’s beards for men

The other side of the coin, regarding how other men feel about beards, is a lot clearer. “Beards certainly enhance men's looks of formidability and make them seem more angry, cranky and masculine,” says Brooks. “So it's probably a huge advantage when that kind of signaling is really important.”

In our complex modern life, with money, technology, and a stratified social system, the biological signaling of a beard may have diminished somewhat. But curiously, men still respond to broader social conditions by putting down the razor.

“The proportion of men who grow facial hair goes up when things are politically uncertain,” says Brooks. “When the economy tanks, beards go up. The rise of beards in western societies that were largely clean-shaven in recent years likely had some of its genesis in the 2008 global financial crisis.”

And for men who can’t grow a beard, even during a recession, research shows you shouldn’t stress about impressing women, says Brooks. “If there are heaps of beards around, being clean-shaven is more attractive, and if there are heaps of clean-shaven men around, beards are more attractive. It's not like a particular style is ever going to be the best.”

So if you struggle to produce stubble, just take it on the chin. It doesn’t make you any less of a man.

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